SIMBAD references

We report the detailed analysis of the X-ray properties of the discrete sources detected in a long (72 ks) Chandra ACIS-S observation of the Antennae galaxies. We detect 49 sources, down to a detection limit of ∼10³⁸ ergs.s^–1; 18 sources have L_X>10³⁹ ergs.s^–1 (ultraluminous X-ray sources; ULXs). Six of the 49 sources have an extended component. Two sources show evidence for variability during this observation, and three sources exhibit long-term variability in timescales of a few years. The spectra of the discrete sources are diverse, suggesting different emission mechanisms, broadly correlated with the source luminosity: the most luminous sources exhibit harder emission, while the spectra of fainter sources appear softer. Spectra and variability suggest that the ULXs may be binary accretion sources; Supernova remnants or hot interstellar medium in the Chandra beam may be responsible for some of the softer sources.